The Irish Republic was the Irish state set up by Dáil Éireann, the illegal assembly made up of the majority of Irish MPs elected in the British general election in 1918.

It origins dated back to the Easter Rising of 1916, when a small minority of Irish republicans under Padraig Pearse seized key locations in Dublin and proclaimed an Irish Republic. Though this insurrection was crushed, and at the time had little public support, its surviving leaders, notably Eamon de Valera seized control of a small monarchist party, Sinn Féin that had wrongly been credited by the British Government and the people with being behind the Rising, and used it as a vehicle to campaign for a republic. It won a clear majority of (largely uncontested) seats in the 1918 general election and formed the Assembly of Ireland (in gaelic, Dáil Éireann) in Dublin. The Dáil first assembled in the Mansion House in Dublin in January 1919.

From 1919 to 1921 the Irish War of Independence was fought, between the Irish Republican Army (the paramilitary army of the Irish Republic) and British forces, notably the notorious Black and Tans (former soldiers specially recruited, who wore uniforms of blan and khaki, hence the name). Both sides carried out brutal murders; The Black and Tans burned entire villages and massacred ordinary civilians, while the IRA burned historic buildings and mounted a form of ethnic clensing against protestants, particularly in the Munster area. (They even tried to burn down historic Carton House, the home of the eighteenth century Irish patriot and rebel, Lord Edward Fitzgerald until a family member reasoned with them!)

The largely Catholic police force, the Royal Irish Constabulary found itself caught in the middle; murdered by the IRA as part of the Crown forces, while trying to restrain and halt by brutality of the Black and Tans. By 1921, the IRA, as its senior strategist, the Irish Republic's Minister for Finance, Michael Collins admitted, was on the brink of collapse. Luckily however, the British government did not realise how close they were to victory, and offered a Truce which the astonished Irish leaders accepted.

In December 1921, negotiators from the Irish Republic's government, led by Griffith and Collins and the British Government team under Prime Minister David Lloyd George and including Winston Churchill, signed the Anglo-Irish Treaty, replacing the Irish Republic with a new dominion called the Irish Free State. The leadership of the Republic split between pro and anti-treatyites, the latter under the leadership of resigned president Eamon de Valera. However the public clearly was in favour of the Treaty and the new state. The Civil War ended in 1923.

The Irish Republic had a short existence. It is difficult to work out exactly what public support it had, for of the two elections that took place during its existence, in 1918 and 1921, the former saw most seats won without a contest, while in the latter all seats but four were elected unopposed. Whether that was because of genuine public support or fear of challenging Sinn Féin and in particular the IRA is impossible to guess. Accounts have come to light of by-elections being won by Sinn Féin in 1917 and 1918 because, in one notorious case, a gun was placed to the head of Returning Officer about to announce the victory of a non-Sinn Féin candidate and he was told to 'think again'. (He recounted and 'found' extra votes that 'gave' the seat to Sinn Féin.) A recent Irish academic study, on the basis of examining voting patterns in contested seats, in contested by-elections and in local government elections, concluded that Sinn Fein had the support of somewhere between 45% and 48% of the electorate.

But given the likelihood that a large proportion of voters supporting the party did not necessarily agree with its policy platform (a common occurrence in democracies, where votes may be gained through (i) support for popular candidates irrespective of policy, (ii) voters who join a perceived 'bandwagon', (iii) people being turned off by rival parties and so vote for the 'least worst option', (iv) personal reasons separate from national agendas) it seems likely that probably no more than one in three Irish voters in 1918 supported the idea of UDI (Unilaterally Declared Independence), with the vast majority accepting for some form of workable self government short of an independent republic. Such analysis reflects contemporary records and memories of those who lived in the period, who spoke of the vast majority of people in their areas being either indifferent, unenthuastic or moderate in their views, with only small groups (whether Sinn Féin, the Irish Parliamentary Party[?] or unionists) being passionately committed to a 'cause'.

Though the leaders tried to set up a functioning parliament and government, the Irish Republic never was internationally acknowledged as a legitimate regime by any state in the world. Efforts by President de Valera in the United States and the Republic's 'ambassador' at the Versailles Peace Conference after World War One, Sean T. O'Kelly to get international recognition failed. According to international law, and even most Irish historians, the real government in Ireland from 1919 to 1921 continued to be the British Dublin Castle regime under the Chief Secretary of Ireland[?] (the British cabinet minister who effectively headed the Dublin Castle administration) and the nominal head, Lord Lieutenant of Ireland, the King's representative. Even some of those who fought to 'preserve the Republic' and abandon the Anglo-Irish Treaty in the Irish Civil War (1922-23), most notably Eamon de Valera, later admitted that their opposition to the Anglo-Irish Treaty and the Irish Free State was a mistake. (De Valera answerably unambiguously 'opposing the Treaty' when asked near the end of his life by someone 'what was your biggest mistake?')

Speaking in Dáil Éireann in the 1990s, current Taoiseach (prime minister) and leader of the anti-treaty Fianna Fáil party, Bertie Ahern, admitted that the real date from which Irish independence should be measured, isn't 1919 and the formation of the Irish Republic but 1922 and the formation of the Irish Free State, the first internationally recognised, legally legitimate Irish State.